Method of making a resin-molded motor

ABSTRACT

A resin-molded motor constituted by a rotor, a laminated stator having generally axially and radially extending slots defining pole pieces therebetween and resin material molded in the inner portions of the slots and over the inner ends of the slots for insulation and bonding of the laminated stator, a generally cylindrical resin material shroud at each end of the stator extending from the corresponding axial end face at the inner peripheral portion thereof and extending axially of the motor, a steel sheet bracket on the axially outer end of each of the shrouds and having journal means therein supporting the rotor, a plurality of windings around the pole pieces of the stator and having axially outer coil ends against the shrouds, a connector having connector terminals to which conductor ends of the windings are connected for supplying power to the windings, and a housing of resin material molded around the stator, the windings, the shrouds, the brackets and the connector with the terminals exposed from the housing.

This is a divisional application of Ser. No. 07/406,356, filed Sep. 12,1989, now U.S. Pat. No. 5,134,327.

BACKGROUND OF THE INVENTION

The present invention relates generally to a resin-molded motor and amethod of manufacturing it.

A resin-molded motor, such as a compact induction motor commonly used ina home washing machine, comprises a resin-insulated core winding, astator with a winding, and a rotor accommodated in a resin housing. Inthe conventional resin-molded motor, as disclosed in Japanese laid-openpatent application 79207/1977; a non-magnetic cylindrical member isdisposed at each end of a magnetic pole member of the stator and saidmagnetic pole member and a yoke member are spray-coated with a resincomposition to insulate the winding portion of the stator and, at thesame time, to secure said cylindrical member to the end face of thestator. After the winding is formed, the whole assembly is covered witha molded resin, i.e. resin-molded, housing.

As described in the above patent literature, the cylindrical member ofnon-magnetic material which is disposed at each end is intended toprevent the coil end of the winding from passing across the core centerand to prevent inflow of the molding resin composition into the rotorsegment and the resin coating is intended to bond the members into anintegral unit, insulate the stator and secure the punched-out statormembers in position.

However, since the cylindrical member has the same inner diameter assaid stator members so as to permit insertion of the rotor, the coil endtends to expand outwardly where the primary coil overlaps with thesecondary coil so that the ineffective part of the coil is increased tocause such problems as increased electric resistance, increased coilrequirements and increased weight. Moreover, unless the outer diameterof the magnetic pole member of the stator is increased, the yoke membercannot be inserted into the magnetic pole member so that the overallsize and weight has to be increased.

Furthermore, although the individual stamped-out core members laminatedand bonded have been secured in position at the slots by the resincoating, the magnetic pole portions along the inner circumference facingthe rotor are interconnected in the form of a ring and, therefore, notsecured by the resin coating, with the result that the overallmechanical strength is not sufficient and the resin may crack and causean insulation failure. Moreover, because of the bridging of magneticpoles, the electrical characteristics of the motor are alsounsatisfactory.

It is therefore the object of the present invention to provide aresin-molded motor having improved characteristics and reduced bulkwhich have been achieved by improvements in the construction of thestator and cylindrical member.

SUMMARY OF THE INVENTION

A resin-molded motor according to the invention comprises a rotor and alaminated stator with the slots, inner edges and ends thereofresin-molded for insulation and bonding, a generally cylindrical resinshroud disposed at each end of said stator, a sheet steel bracket havingjournal means for supporting a bearing for a rotor, windings around saidstator, the coil ends of said windings being connected to connectorterminals, and a frame covering said stator, windings, shroud andbracket and molded together with said connector by a synthetic resincomposition.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partial cross-section view showing the construction of aresin-molded motor embodying the principle of the invention;

FIGS. (a) and 2(b) are perspective views showing the construction ofmagnetic pole members;

FIG. 3 is a perspective view showing the construction of a yoke member;

FIG. 4(a) is a partial cross-section view showing a resin shroud moldedaround the magnetic pole member and FIG. 4(b) is a perspective view ofthe same;

FIG. 5 is a diagrammatic view of the stator having the windings thereonas viewed from the coil end;

FIG. 6 is a perspective view of a bracket; and

FIG. 7 is a cross-section view of the metal mold used for molding theframe.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

A preferred embodiment of the invention is described in detailhereinafter, reference being made to the accompanying drawings.

The stator of the resin-molded motor of the invention comprises anexternally disposed yoke member 2 and an internally disposed magneticpole member 3. As illustrated in FIG. 2(a), the magnetic pole member 3comprises one to three units 7 stamped from a core sheet and eachcomprising a plurality of magnetic poles 4 interconnected at the innerends thereof by connections 5 to form a ring with recesses 6 formedalong the inner circumference of the ring at positions corresponding tothe respective connections. On the other hand, an assembly 8 of coresheets into independent magnetic poles 4' as shown in FIG. 2(b) isprovided each having the same thickness as a rotor 9 and disposed inalignment with the magnetic poles 4 and the opposite ends of poles 4'are secured to poles 4 by means of half-punched out fitting grooves 10.

The yoke member 2, as shown in FIG. 3, is a core 11 in the shape of aring with radially inwardly extending projections 14 provided withnotches 13 on the inner ends and which are adapted to fit into the slots12 between poles 4 and between poles 4' of the magnetic pole member 3and has the same thickness as the magnetic pole member 3 and is securedin position around the pole member 3. The thus laminated and securedmagnetic pole member 3 is clad by molding an electrically insulatingsynthetic resin (hereinafter referred to as resin) such as polyethyleneterephthalate or polybutylene terephthalate therearound to forminsulating layers in the slots 15 and at 16 at the inner edges ofassemblies 8 and the windings at 17 at both ends of the pole member 3and strengthen the bond between units 7 and assemblies 8. Furthermore, agenerally cylindrical shroud 18 is simultaneously molded at one end faceof the magnetic pole member 3. This shroud 18 is shaped in a generallycylindrical form which is slightly longer than the extension of the coilends of the winding. The inner diameter of one portion is equal to theinner diameter of the magnetic pole member 3 and the corresponding outerdiameter is equal to that of the slot region 16, while the innerdiameter and outer diameter of the other portion are relatively smallerand, as shown in FIG. 4(b), the forward end face has a ring-shapedgroove 20 therein with a plurality of radially outwardly extendingpocket-shaped portions 21. As shown in FIG. 5, each of the pocket-shapedportions 21 is disposed in a position between windings 22a and 22b wherethe magnetic pole is situated so as to avoid interference of coil end19a.

The magnetic pole member 3 insulated and provided with the shroud 18 byresin molding is provided with windings 22a and 22b, and 23a and 23b insuch a manner that the coil end 19a will fit the shroud 18 as shown inFIG. 5, and after insertion of wedges 24, the yoke core 2 ispress-fitted to the outer periphery of the magnetic pole member 3 toform a stator 25. Disposed on an axial end face of the stator 25 is aconnector 26 and the ends of said windings are connected to connectorterminals 27 thereof, respectively.

Fitted into the ring-shaped groove 20 of shroud 18 of the thusconstructed stator 25 is a bracket 28 of sheet steel as shown in FIG. 6.This bracket 28 is provided with projections 45 along its edge forfitting into said pocket-shaped grooves 21 and preventing slip-out andmovement in the direction of rotation after molding.

Furthermore, a wall portion 29 external of said ring-shaped groove 20and pocket-shaped grooves 21 insures insulation from coil end 19a.

Then the rotor 9 in inserted into the internal bore of the stator 25 anda first bearing 30a is supported by a journal means 31 in the bracket28. Then a shroud 32 molded from resin in the same shape as shroud 18 isjuxtaposed with the other end face of the magnetic pole member 3 and abracket 33 is fitted to the end thereof just as the bracket 28 and asecond bearing 30b of the rotor 9 is supported thereby. Then the coilend 19b is trimmed to insure intimate contact with the shroud 32.

The finishing process for the thus constructed resin-molded motor isdescribed below. The above-described stator 1, brackets 28 and 33,connector 26 and rotor shaft 36 are set in a metal mold 34, 35 having aparting plane X--X' and the resin material is poured in to mold a casing37 and a flange 39, whereby the resin-molded motor shown in FIG. 1 isobtained.

In order that the resin will not flow into the rotor space or otherunwanted parts during the molding process, the end faces of brackets 28and 33 are respectively formed with ring-shaped projections 40 to pressagainst the mold components 34 and 35 and thereby fine-adjust thepressure in the pressing direction on the respective component members.The brackets 28 and 33 are provided with spigot means 41 for ease ofsetting in the mold and equalizing the air gap for the rotor 9 andstator 25. This is to absorb any dimensional error of the inner andouter diameters of the journal means 31 in the press forming of brackets28 and 33 and the journal means 31 is thereby assured of having anaccurate inner diameter. With this dimension as a reference, the spigotportion 41 is processed to ensure accuracy of the outer diameter toalign the center of the bearing with the mold center. Furthermore, themetal mold components 34 and 35 are provided with a plurality of blades42 adapted to abut the coil ends 19a and 19b so as to prevent exposureof coils through the resin on the surface of the casing caused by theshift or deformation of coil ends 19a and 19b due to the moldingpressure. During molding, the blades form ventilation orifices 43 toenhance the dissipation of heat from the windings 22 and 23.

The niches or grooves 13 formed in the projections 24 of the yoke member2 provide for local flows of resin to assure a smoother resin flowaround the wedges 24 and relieve the axial pressure on the wedges toprevent dislocation of the wedges 24.

Thus, the bridge-free magnetic pole member according to the inventionassures tougher lamination and bonding and facilitates the fitting ofthe yoke and enables the provision of a resin-molded motor free of noiseand vibration and having improved output characteristics.

Furthermore, the tapered shrouds not only prevent expansion of the coilend toward the outer diameter and reduce the winding materialrequirements but help reduce the diameter of the stator and the overallsize of the resin-molded motor.

In addition, the blades at the coil end region of the metal mold reducethe incidence of rejects due to exposure of the coil on the surface andthe ventilation orifices formed thereby contribute to enhanced heatdissipation from the windings.

Furthermore, because the connector fitting plane is disposed in theaxial direction, the entry of water and water droplets is prevented whenthe motor is used with the shaft down, in a washing machine, forinstance.

What is claimed is:
 1. A method of producing a resin-molded motorcomprising disposing a punched-out stator member with independentmagnetic poles between a couple of units of punched-out core member withmagnetic poles interconnected at inner edges of its slots to form aring, laminating said members, cladding said slots, inner edges and endsof the assembly by resin molding for insulation and bonding to fabricatea magnet pole member, forming a generally cylindrical synthetic resinshroud, the inner diameter of which is equal to that of the magneticpole member and the outer diameter of which is equal to that of theinsulation layer at the bottom of the slot, with the inner and outerdiameters being tapered toward the tip, with the length of the shroudbeing slightly greater than the length of the coil end, applyingwindings to said magnetic pole member, connecting the coil ends ofwindings to connector terminals, inserting wedges, fitting projectionsof a yoke member having cut-out groves for passage of resin along itsouter periphery into the slot openings of the magnetic pole member toform a stator, disposing a separately molded shroud of the same shape asthe first-mentioned shroud at the other end face of said magnetic polemember, disposing a sheet steel bracket with journal means forsupporting a bearing for a rotor at the end of such shrouds, applyingwindings to said stator, connecting coil ends of said windings toconnector terminals, and forming a frame for housing said stator,windings, shrouds and brackets and said connector in an integral unit byresin molding.